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LONDON - Despite their fearsome reputation, piranhas are wimps who gather in large shoals to protect themselves from predators, say scientists.
Rather than aggressive killers, research shows piranhas are omnivorous scavengers, eating mainly fish, plants and insects, Anne Magurran of Scotland's University of St Andrews said.
"Previously it was thought piranhas shoaled as it enabled them to form a co-operative hunting group," she said. "However, we have found that it is primarily a defensive behaviour."
Piranhas face constant attack from predators including river dolphins, caiman - a relative of the crocodile - and bigger fish, such as the giant pirarucu.
"Their cautious behaviour is crucial to avoid being eaten," Magurran said.
Her work with the Mamiraua Institute in Brazil shows how shoal sizes increase in relation to predation risk, especially when water levels in the Amazon basin are low, giving piranhas less room to escape attack.
- REUTERS
